In a conventional position detection apparatus, a magnetic element, such as a permanent magnet, or a magnetic detection element, such as a hall effect element, is equipped to a target. When the target whose rotation angle is to be detected starts to rotate, the magnetic detection element detects a magnetic flux density in order to detect the rotation angle of the target. For example, in a position detection apparatus disclosed in JP 3491577 B2 (corresponding to US 6498479 B1), a magnet is equipped to a shaft whose rotation angle to be detected. The shaft is also referred to as a target. When an output voltage from a hall effect element is defined as VH (unit: volt), and a maximum value of the output voltage from the hall effect element is defined as V0 (unit: volt), the rotation angle θ (unit: degree) of the shaft is calculated by the following expression 1.θ=sin−(VH/V0)   Expression 1
In the above position detection apparatus, during an assembling process, the magnet and the hall effect element may be shifted from predetermined positions and a position shift may be generated between the hall effect element and the magnet. Thus, an accuracy of the rotation angle θ calculated by expression 1 may be degraded. In order to correct the positions of the magnet and the hall effect element, a position inspection process may be added to the assembling process. However, the number of processes is increased when the position inspection process is added.